Articles of Incorporation are generally considered public records that anyone can access. Sending him a copy is not giving him anything that he could not get from the Secretary of State's office anyway.
If what he wants to do is verify that you are legit, that is a corporation in good standing, he should verify that for himself directly with the Secretary of State's office. After all, if you were trying to lie to him and pull something shady, why would you necessarily send him a real copy of the articles rather than a made up version?
Of course any serious investor will want to see far more than that before investing substantial amounts of money. They will want to see all your books and records including tax returns to verify that all is in good order.